In industrial settings such as plants, factories, or other large-scale systems that utilize three-phase power, there can be numerous problems caused by voltage transients present in one of the three-phase circuits. These transients may be caused by switching occurring at an upstream power-station, arcing ground faults, lightning strikes, or numerous other events. Such transients can severely damage or destroy equipment connected to the effected three-phase circuit, or, when the system employs circuit interrupters, can cause those interrupters to open the circuit, resulting in power outages throughout the plant. Such outages have negative economic effects since productive equipment remains non-functional until the circuit is re-energized. Moreover, in settings where uninterrupted power is critical for safety or other reasons, such as on ocean-going vessels where control surfaces must remain powered to navigate the vessel, such outages are not acceptable.
Transient voltage surge suppression has been in use for over thirty-five (35) years. However, the prior art systems have several shortcomings. Metal oxide varistors (MOVs) and silicon avalanche diodes (SADs) clamp voltage surges only after the voltage is double that normally present in the circuit or more. Such a system causes stress on devices connected to the circuit and may damage or cause permanent failure of the components. Additionally, the solid state components used in the prior art systems are degraded by the transient events that the circuit is designed to protect against.